Human Th17 cells produce a soluble mediator that increases podocyte motility via signaling pathways that mimic PAR-1 activation

Abstract

The specific pathogenesis of idiopathic nephrotic syndrome (NS) is poorly understood, and the role of immune mediators remains contentious. However, there is good evidence for the role of a circulating factor, and we recently postulated circulating proteases as candidate factors. Immunosuppressive therapy with glucocorticoids (GCs) and T cell inhibitors are widely used in the clinical treatment of NS. Given that T helper (CD4+) cells expressing IL-17A (so-called Th17 cells) have recently been reported to be resistant to GC treatment, and GC resistance remains a major challenge in the management of NS, we hypothesized that Th17 cells produce a circulating factor that is capable of signaling to the podocyte and inducing deleterious phenotypic changes. To test this, we generated human Th17 cells from healthy volunteers and added the supernatants from these T cell cultures to conditionally immortalized human podocytes in vitro. This demonstrated that podocytes treated with Th17 cell culture supernatant, as well as with patient disease plasma, showed significant stimulation of JNK and p38 MAPK pathways and an increase in motility, which was blocked using a JNK inhibitor. We have previously shown that nephrotic plasma elicits a podocyte response via protease-activated receptor-1 (PAR-1). Stimulation of PAR-1 in podocytes elicited the same signaling response as Th17 cell culture supernatant treatment. Equally, protease inhibitors with Th17 cell culture treatment blocked the signaling response. This was not replicated by the reagents added to Th17 cell cultures or by IL-17A. Hence, we conclude that an undefined soluble mediator produced by Th17 cells mimics the deleterious effect of PAR-1 activation in vitro. Given the association between pathogenic subsets of Th17 cells and GC resistance, these observations have potential therapeutic relevance for patients with NS.

Major histocompatibility complexes are up‐regulated in glomerular endothelial cells via activation of c‐Jun N‐terminal kinase in 5/6 nephrectomy mice

“…MAPK-JNK, but not MAPK-p38, participates mainly in IFN-γ-induced antigen presentation, including CIITA and genes encoding MHC Class II molecules in macrophages (Valledor et al, 2008) and brain endothelial cells (Adamski & Benveniste, 2005). In the present study, IFN-γ infiltrating T lymphocytes, suggesting that MAPK-JNK is also involved in signal integration during costimulation of T lymphocytes (Li, Whaley, Mondino, & Mueller, 1996;Su et al, 1994), including Th17 cells (May et al, 2019). The inactivation of Th1 and Th17 cells following inhibition of JNK signalling is most likely due to the direct inhibitory effects on lymphocytes, lower MHC complex expression on the glomerular endothelial cells or both.…”

“…However, inhibition of NF‐κB reduced the phosphorylation of JNK in cells stimulated with IFN‐γ, but not TNF‐α, suggesting that IFN‐γ and TNF‐α trigger different signalling pathways in the regulation of MHC molecules. JNK inhibitors reduced TNF‐α and IL‐17 expressions in infiltrating T lymphocytes, suggesting that MAPK–JNK is also involved in signal integration during costimulation of T lymphocytes (Li, Whaley, Mondino, & Mueller, 1996; Su et al, 1994), including Th17 cells (May et al, 2019). The inactivation of Th1 and Th17 cells following inhibition of JNK signalling is most likely due to the direct inhibitory effects on lymphocytes, lower MHC complex expression on the glomerular endothelial cells or both.…”

The Th17/IL-17 Axis and Kidney Diseases, With Focus on Lupus Nephritis

“…On podocytes, an experimental study raised the possibility that Th17 cells would produce a soluble mediator that enhances podocyte motility, causing rearrangement of the actin cytoskeleton and increased permeability (136). This finding may be the basis of the correlation found between IL-17 levels and proteinuria and its severity (50, 53).…”

“…This finding may be the basis of the correlation found between IL-17 levels and proteinuria and its severity (50, 53). According to the study, this soluble factor mimics the protease-activated receptors-1 (PAR-1) activation signaling pathways (136).…”

“…In an experimental study, punicalagin (a bioactive antagonist of PAR2) ameliorated lupus nephritis, in association with a significant reduction in splenic Th17 populations compared to the vehicle controls (265). Remembering that PARs are involved in Th17-induced rearrangement in the cytoskeleton and increased permeability (136). In an experimental study with MRL/lpr mice, a traditional Chinese medicinal formula suppressed the IL-17 production and Th17 activity by inhibiting the expression of CaMK4, which was associated with a decrease in renal hypercellularity and infiltration by neutrophils (266).…”